1. Field of the Invention
The present invention relates to a disk apparatus for recording in and/or reproducing information from a rotating disk-shaped medium and an actuator holding method for holding an actuator, which has a recording and/or reproducing head mounted on its distal end, in a parking position.
2. Description of the Related Art
Conventionally known is a magnetic disk apparatus that comprises a spindle motor for rotating a magnetic disk and a voice coil motor (see Jpn. Pat. Appln. KOKAI Publication No. 7-176152, for example). The voice coil motor swings an actuator, which has a magnetic head mounted on its distal end, thereby moving the magnetic head substantially in the radial direction of the disk.
In operating the magnetic disk apparatus, the magnetic disk is rotated by means of the spindle motor, and the actuator is swung by means of the voice coil motor. Thereupon, the magnetic head on the distal end of the actuator is moved substantially in the radial direction of the disk, and the head is opposed to a desired track of the disk. In this state, information is recorded on and/or retrieved from the track.
The magnetic disk apparatus is provided with a retracting and locking mechanism that retracts and locks the actuator to the inner periphery of the disk when not in operation. By locking the actuator to the inner periphery of the disk by means of the retracting and locking mechanism, the magnetic head can be prevented from unexpectedly moving to an effective region of the magnetic disk and from touching the disk when the actuator is not operating.
The retracting and locking mechanism includes a movable permanent magnet fixed integrally to the rear end portion of the actuator and lower and upper fixed yokes that vertically hold the permanent magnet between them. The permanent magnet and the lower and upper yokes constitute a magnetic circuit for urging the actuator toward the inner periphery of the disk. As the actuator rotates, the movable permanent magnet moves along a gap between the lower and upper fixed yokes.
The gap between the lower and upper fixed yokes is gradually narrowed toward a lock position for the actuator so that a maximum magnetic force acts on the movable permanent magnet in the lock position. Thus, the actuator can be securely locked in the lock position.
In operating the actuator, however, it must be unlocked. Therefore, the magnetic retention of the actuator in the lock position must be set to a value lower than a specific magnetic force such that the actuator can be unlocked. If the retention exceeds this specific force, the actuator cannot move from the lock position.
Thus, if an undesired vibration is applied to the actuator in a nonoperating state from outside the magnetic disk apparatus, the aforesaid retracting and locking mechanism inevitably allows the actuator to move easily from the lock position.
Further, the retracting and locking mechanism of this type includes the lower and upper fixed yokes that are long enough to cover the whole movement region of the movable permanent magnet (i.e., whole swinging range of the actuator). When information is recorded or reproduced by means of the magnetic head on the distal end of the actuator, therefore, a retractive force that is directed to the inner periphery of the disk continually acts on the actuator. Accordingly, this conventional mechanism has a problem that the continually acting retractive force exerts a bad influence upon the seeking operation of the magnetic head, and therefore, upon information recording and/or reproducing operation.